Abstract:Rising sea level poses a major risk to human societies and coastal habitats and ice sheet melt will be a major contributor to sea level rise. Thus, we must understand uncertainty of forcing and variability within the climate system affecting ice sheet melt to assess long-term risk. The predictability of polar climate is limited by uncertainties in the given forcing, the response to this forcing, and the internal variability of the fully coupled climate system. Given these factors, the proposed study comprises three broad scientific questions: (1) Would internal climate variability affect ice sheet evolution? (2) How ice sheet topography influences atmosphere? (3) What are the uncertainties of estimating polar climate response to anomalous sea surface temperature (SST)? Internal variability is one of the key features of the climate system arising from feedbacks between internal processes. We estimate how internal variability affects ice sheet projections when atmospheric and oceanic fields are applied as driving force from a large ensemble Community Earth System Model (CESM) simulations differing in initial conditions. We find that some ensemble members show extreme features and we propose to study how internal variability influences ice sheet evolution spatially and temporally through model simulations. From these, we can assess sensitivity of the ice sheet model to internal variability of climate fields and associated uncertainties. To understand atmospheric responses to external forcing, we propose to study two aspects. First, how decreasing ice sheet topography changes circulation patterns, and second, how anomalous SST patterns influence polar climate and ultimately impact ice sheets and polar feedbacks. Using different versions of Community Atmospheric Models, we assess the capabilities of multiple atmospheric general circulation models (AGCMs) to respond to SST forced changes by perturbing SST fields that influence polar climate. By decomposing uncertainties, we address the impact of various physics and resolutions in climate models. From large-ensemble model simulations, we estimate the Global Teleconnection Operator (GTO) for each AGCM to diagnose the sensitivities of polar climate to the boundary condition forcing from anomalous SSTs patterns. This study provides an efficient tool for exploring polar climate response as a first-order assessment of the climate variability driven by SST forcing and the model uncertainties using large-ensemble simulations.